I saw this odd trail on 2 separate nights, near same Deer Lick Galaxy target. It is not fireworks. I too at first suspected a mount issue, combined with a probably slow moving satellite, but seems odd that I have never seen this kind of artifact before, if it is due to my mount. The star eccentricity is roughly orthogonal to trail, and by eyeball the magnitude of the eccentricity is 'in the ballpark' of the trail peak to trough amplitude. So that supports the mount issue explanation. But if it is a mount issue, sort of odd that no one else has ever seen such an artifact (as far as I know), and I have numerous other satellite trails that are all straight (although they may be much faster moving satellites). If the wiggle was due to mount, that sine wave wiggle would make star image somewhat bimodal; whether my stars show that is not so obvious(most don't seem to, some others are arguable). Also, I don't know the time periodicity of wiggle;I only know that exposure was 5min, that trail extends across the full image, so we only know that ~200 cycles(eyeball) occur in photo, and occur in less than 300sec, so cycle upper limit is ~1.5sec. (My mount is an Ioptron CEM60.) Also I just now noticed a fainter trail in the very same image (attached), and it does NOT exhibit the wiggle. (See bottom right corner faint trail.) So if both satellites traveling at same angular speed, then issue unlikely to be the mount. But may be the satellites were travelling at different speeds - I have no idea.
...... and now as I am searching more, I found someone else reported something very similar in Cloudy Nights, on an Ioptron CEM70: www.cloudynights.com/topic/773952-wobble-in-satellite-trail/
They seem to think it was an Ioptron issue. I think I will have to do a more quantitative analysis(eg PSF) on my stars and my other images, to see if I agree.